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Date: Mon, 21 Aug 2017 19:54:02 +0000 (UTC)
From: "ASF GitHub Bot (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (DRILL-5546) Schema change problems caused by
 empty batch
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archived-at: Mon, 21 Aug 2017 19:54:13 -0000


    [ https://issues.apache.org/jira/browse/DRILL-5546?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16135706#comment-16135706 ] 

ASF GitHub Bot commented on DRILL-5546:
---------------------------------------

Github user paul-rogers commented on a diff in the pull request:

    https://github.com/apache/drill/pull/906#discussion_r134299504
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/ScanBatch.java ---
    @@ -329,9 +326,11 @@ public TypedFieldId getValueVectorId(SchemaPath path) {
     
       @VisibleForTesting
       public static class Mutator implements OutputMutator {
    -    /** Whether schema has changed since last inquiry (via #isNewSchema}).  Is
    -     *  true before first inquiry. */
    -    private boolean schemaChanged = true;
    +    /** Flag keeping track whether top-level schema has changed since last inquiry (via #isNewSchema}).
    +     * It's initialized to false, or reset to false after #isNewSchema or after #clear, until a new value vector
    +     * or a value vector with different type is added to fieldVectorMap.
    +     **/
    +    private boolean schemaChanged;
    --- End diff --
    
    Using a flag is very messy. The new version uses a counter. An observer simply remembers the previous count and compares it against the current count. Allows multiple observers without negotiating over which is responsible for resetting the flag.


> Schema change problems caused by empty batch
> --------------------------------------------
>
>                 Key: DRILL-5546
>                 URL: https://issues.apache.org/jira/browse/DRILL-5546
>             Project: Apache Drill
>          Issue Type: Bug
>            Reporter: Jinfeng Ni
>            Assignee: Jinfeng Ni
>
> There have been a few JIRAs opened related to schema change failure caused by empty batch. This JIRA is opened as an umbrella for all those related JIRAS ( such as DRILL-4686, DRILL-4734, DRILL4476, DRILL-4255, etc).
>  


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